1. Field of the Invention
The present invention relates to opto-electronic monitors for monitoring the quality of a liquid in a pool, a spa, a fish tank, a water reservoir, or a water flow system, and more specifically relates to monitors which can automatically measure various concentrations in the liquid and display their concentration on a low-maintenance and continuous basis.
2. Background of the Invention
In hot summer days, dipping into a swimming pool or a spa is one of the greatest enjoyment in life. Swimming is also known as one of the best exercises in the U.S., where there is a very large number of private swimming pools and spas in American families, schools and public facilities. However, what has been grossly overlooked by the millions of pool users is that no one seems to be able to obtain an accurate and up-to-date reading on the quality and sanitary condition of the water in the pool. While supposedly the water is periodically tested by the pool crew, the quality can drastically deteriorate in a very short time due to contamination.
The pool industry has not responded to this concern very well. In fact, the potential health risk has largely been overlooked and ignored. If anything, it would be quite comforting for pool users to know the quality of the water just before they dive in all the time. So far, pool users have mainly relied on the diligence of the pool crew for their own health risk, as they have no other way of ascertaining the quality of the pool. Or, the more naive ones have found comfort by relying on the fact that there are already people in the pool and they seem to be doing just fine.
Unbeknownst to the population, a pool may have bacteria and algae if not properly and regularly treated with chemicals or additives. Prolonged exposure to these harmful elements will adversely affect the eyes, skin, hair and eventually the overall well-being of every pool user. To ensure the overall well-being of the user population, it would be desirable to have an on-site pool water monitoring device for accurately determining the concentration of the main contaminants, namely acidity, chlorine, alkalinity, calcium, magnesium, iron, and bromide, in the pool water.
There are generally three types of water monitoring devices in the pool industry. One of them is the chemical-based indicators, in either solution or dip-strip substrate form, which are widely used by private pool owners due to their low cost. However, this type of indicators, which is based on visual observation of color comparison using standard solutions, is inconvenient and often gives inaccurate results. Most pool owners use this type of monitors to check pool water quality once every week. To ensure excellent water quality on a constant basis, pool owners or users will have to check more frequently or around the clock.
The second type is a hand-held electrode-based monitor which uses un-equilibrium electronic charge transfer or electrochemical potential between the pool water and the electrolytic cell through a membrane. Again, this type of indicator has proven fundamentally unsuitable for continuous on-site measurement. The third type of monitors is an optical-based monitor as described in an U.S. Patent issued to Saaski, et. al., U.S. Pat. No. 5,039,492. This type of monitors employs an optical method based on the resulting color change of an indicator substrate to measure the pH and gas concentrations in sampling blood. Although this method also is derived from the same general optical principle, it is intended for only one time use and not for continuous use in a pool or spa environment.
Therefore, it would be desirable to have an on-site water monitor for continuously monitoring the quality of the pool water on a low-cost, low-maintenance basis.